heya fellas,
i've hexedited the clean rom and it doesn't run on R4 1.18, or YSmenu. and by not run i mean black screen after selecting difficulty. i have not tried the patched version yet. my R4 is the V2 black(not R4"i" and not sdhc). i read on here someone claimed to have it working on an R4, which i find hard to believe, but stranger things have happened. patiently waiting for a solid fix... hang in there fellow R4 users.

I followed the above instructions and so far it's working perfectly on my original R4, I'm only into the tutorials but I can save, quit, load up my saved game and carry on with no problems what so ever.

Djay,
could you please copy and upload the exact firmware your running on your original R4 for kh358?
i used with Ys and my patched 1.18 and the official 1.18 DL from R4 site, and all yielded same result, black screen. i'm quite puzzled now as to why my particular R4 is not working, i've never encountered a problem like this before, and i'm very used to patching roms...and getting them working btw
if you could upload yours, it would help me heaps.
cheers,
Jer

EDIT:
don't worry. i just dl'd the clean rom again. hex edit fix, then worked. i just now ran the hex code of both nds files through a program to check they were identical, they weren't. there were missing lines of code among other things in the original i had. obviously the first dl'd file got corrupted in some way. thanks for listening and helping anyway guys. will start playing after tonights F1. and yeah, running on patched R4 v1.18 firmware, i just don't like the look of that YSmenu, and until i 'need' to switch to it, plain ol' 1.18 will do fine. i really don't know why people bash the R4 so much, this is the first real problem i've ever had trying to run a game, and turns out it wasn't even the R4, bad rom.

Instructions:
1. Extract all of the contents of the RAR file to a path of your choice.
2. Place your clean, untrimmedKingdom Hearts 258/2 Days (U) rom inside the "rom" folder.
3. Double-click patch.bat (when it says "press any key to continue" you need to do so, of course.)
NOTE: You might need to right-click the file and select "Run as Administrator" if you're using Windows Vista/7 with UAC (User Account Control) on.
4. The patched rom will be called patched.nds. Feel free to rename it - don't forget to leave the file extension part .nds in the title (duh!), then transfer it to your flashcart.
5. Enjoy the game

.....

Tried on R4, works perfectly up to now!This fix does exactly the same thing that the guide in this thread says,
so it works for the same flashcarts that the guide works for.

at first i got black screen after selecting difficulty with the clean untrimmed file. i used the first patch and it worked with no problem! Very nice graphics for a DS game, with nice music & voice acting, I'm impressed.

Ok, I really need your help guys, seeing as you all got it to work properly. I did the hexing thing, i put the game on my M3DS real, and started playing. It doesn't crash at the beginning, but when I'm trying to save my game, all three slots say something about corrupt data. And as soon as I click on save, the game freezes. The music keeps on playing, but it jusn't stop saving. What am I doing wrong? I wanna play! O.O

Ok, I really need your help guys, seeing as you all got it to work properly. I did the hexing thing, i put the game on my M3DS real, and started playing. It doesn't crash at the beginning, but when I'm trying to save my game, all three slots say something about corrupt data. And as soon as I click on save, the game freezes. The music keeps on playing, but it jusn't stop saving. What am I doing wrong? I wanna play! O.O

EDIT: Crap, I clicked one time too many. Sorry for doublepost.

EDIT2: After some more surfing and searching for a solution, I decided to update my system firmware to Sakura 1.41. And,, it works! JOY =D